This sort of thing is a waste of money and government resources. It establishes a police state in order to deal with something that isn't actually directly the state's problem. Drug addiction IS a state problem because it can increase welfare recipients (not to mention crime or domestic abuse and family monetary strain), but people spending state money on drugs is not. Drug use, as opposed to abuse, is across all sectors of the economy, poor or rich, and in recreational use seems to have no greater impact on general economic success than say, alcohol or tobacco use, both of which are likewise restricted for purchase by recipients of state welfare benefits. Using the cudgel of welfare beneficiaries in order to impose either a) a further useless gesture of anti-drug policy or b) to attach state mandatory conditions that are punishing morally harmless activity and c) more importantly, treating ALL conditional assistants as though they are suspected of such activities (worse still, in the case of Florida the applicants themselves are required to pay for this police state treatment that other people have imposed upon them already by demanding drug tests, most of which will come back negative)
Certainly there are legitimate reasons to attach some conditional support for government or charitable assistance. Drug testing isn't one of them. If you want to deal with drug use or more importantly drug abuse, start by treating it as a medical problem, not an economic problem. The entire architecture strikes me as a policy that only succeeds because we politically have it out for the poor. Or rather, the poor who we think are poor because they're just all doped out, strung out drug addled morons (or that they're all using these drugs out of irresponsibility rather than because they're unable to get proper mental health care and are self-medicating with booze and crack). Apparently not enough voters and politicians know enough poor people.
Further note: the feeble defence offered by the spokesperson does not work at all. I seriously doubt most drug dealers accept food stamps for example. Sure recipients could sell their food stamps for cash, but I see no problem with that by itself. There are lots of things that can be bought with cash (drugs are one such item of course). Many of which might be desirable and even useful. Food's about the only thing you can buy with food stamps. If you don't need/want more food but you do need/want more money, for fuel or bus fare or clothes for interviews or even for drugs, then this is a good option. Better options would be to just do cash transfers instead of payment in kind but apparently we want poor people to adopt only specific choices that we have pre-approved rather than just give them the money and assume they can make their own (rational) choices to satisfy their wants and needs. You know, like normal human beings.
I would note further, the type of people likely to apply for welfare benefits are unlikely to be the strung-out sort. I never saw it even enter Bubbles' head in the Wire to go to the government at any level for some sort of assistance (he was busy running other scams and selling scrap metal and t-shirts or candy, rather industriously if not exactly prosperous) and consequently you probably won't find many heroin or crack addicts wading through forms to fill out the necessary paperwork to apply for welfare benefits. This is an expected outcome: that a problem that doesn't quite exist will be treated with a sledgehammer because the poor are an unpopular political group. A vile and reprehensible condition being poor is, and clearly no decent person would ever be poor. Only a drug addled moron it seems must be poor.
And then there's reality.